Species i. C. atrella (Townes, 1945)

Adult:

Male terminalia of C. atrella (left)
with superior volsella (right)

Pupa: pupal spur with about one or two major spines, but may be two more smaller lateral spines.

Pupal spur of C. atrella

Larva a small to medium plumosus type (len. female abt 9.4-16.7 mm; male 10.4-11.4 mm), ventral tubules moderately long (ant. 0.84-2.9 mm; post. 0.95-3.45 mm) with posterior pair generally longer.  Posterolateral tubules well developed, 200-400 µm.  Anal tubules relatively long, often partially bilobed, dorsal and ventral pair approximately the same size, length about 633-660 µm, and 3.7 to 4.2 times longer than wide.
Gular region slightly darkened on posterior third or occasionally half, frontoclypeus pale.
Mentum (Fig. c) with rounded teeth, c1 tooth rather narrow, c2 teeth moderately seperated (type IB or III, but often worn); 4th laterals reduced part way or completely to level of 5th laterals (type I-II).
Ventromental plates (Fig. d)separated by about 29-33% of mentum width, with about 39-51 striae; VMR about 0.33-0.35.  Pecten epipharyngis (Fig. a) with about 11-14 relatively broad teeth (type B).
Premandible with inner tooth 3-4 times wider than outer tooth.
Antenna (Fig. b) with basal segment about 3.5-4.7 times longer than wide, RO about 2/5-1/2 up from the base; AR about 2.1-3.2; segment lengths (micron): 144 : 34 : 11 : 13: 7.  The relative lengths of the segments varies considerably in larvae from different areas, a New Mexico larva having a much longer antenna, while a Californian rearing had a shorter antenna, the differences not being obviously related to overall larval size.
Distance between the antennal bases generally less than that between the S4 setae, S4 setae separated by 80-90% of the width of the frontoclypeus.
Mandible (Fig. e) with 3rd inner tooth generally only partly separated and colored (type IIB), and about 14-19 furrows on outer surface at base, about 10-13 setae in the Pecten mandibularis; MTR about 0.34.

Cytology:  4 relatively short polytene chromosomes with thummi arm combination, AB, CD, EF, G.
Centromeres not heterochromatic.  Arm G very short and paired only at the terminal nucleolus, sometimes end-to-end.
Large nucleolus in arm B and a smaller one in arm F at about group 11.    Arm C unpaired in some specimens.
Polymorphism in all arms except G.

Molecular: There is a large amount of MtCOI barcode sequence in the BOLD database.

Found:             Type locality - Reno, Nevada (Townes 1945)
            Alberta - Nordegg (Paratype - Townes 1945)
            Ontario - 'Copanspin Farm' Dunrobin (45.42°N, 75.87°W); 0.5 ml e. Dunrobin (45.42°N, 75.86°W); South March nr Mud Lake
            (44.88°N, 78.27°W) ;Hogs Back (45.37°N, 75.70°W), Ottawa (all Carleton Co.).
            Manitoba - Aweme, Caroll (Paratypes - Townes 1945); Lake Winnipeg (Sæther 2012)
            Prince Edward Island - Brackley Beach, Canadian National Park (Paratype - Townes 1945)
            California - Tahoe City (Paratype - Townes 1945); Lake Davis, Plumas Co.; Fish hatchery Spring Valley, San Diego Co.
            Colorado -Denver; Fort Collins (Paratypes - Townes 1945).
            Indiana - Crooked Lake, Noble Co.
            Massachusetts - Oak Bluffs (Paratype - Townes 1945).
            Minnesota - Lake Christina (46.08°N, 95.75°W), Douglas Co.; Anderson II WPA wetland, Audubon (46.86°N, 95.98°W), Becker Co.
            New Mexico - Eagle Nest Lake (36.55°N, 105.25°W), Colfax Co.
            North Dakota - Fuller Lake; Larimore Dam, Grand Forks Co.; McVille Dam, Nelson Co.; Warsing Dam, Eddy Co.
            South Dakota - Brookings, Erwin (Paratypes - Townes 1945).
            Wisconsin - Reader Farm (45.07°N, 89.42°W), Madison, Dane Co.

            Prairie sloughs, larger pools, and lakes in depths of 0.09-13.5 m.

It is possible that Townes' type series of C. atrella was a mixture of two species: one with a southern distribution e.g. the type from Reno, Nevada; and the other a more Boreal species, e.g the paratypes from Alberta and Manitoba.  This second species is not conspecific with C. ?nr. atrella (below).

Previously Species Ea of Butler, and then C. nr. anthracinus of Butler et al. (1995).  Polytene chromosomes fully described by Martin et al. (2006).  Some of the differences of morphological characters from different localities may be related to the different combinations of chromosome sequences noted between populations, some of which appeared to be related to the depth of the habitat (Martin et al. 2006).  It seems likely that C. atrella is the sister species of C. degelenus Seisebaev, Bakhtin & Siirin (2001) which is known from Kazakhstan.